1. Field of the Invention
The present invention generally relates to vehicle suspension systems including acceleration-sensitive damping. More specifically, the present invention relates to a shock absorber with a fluid flow control arrangement for an acceleration-sensitive damping circuit to be incorporated into the suspension system of a bicycle.
2. Description of the Related Art
Bicycles intended for off-road use, i.e., mountain bikes, commonly include a suspension assembly operably positioned between the rear wheel of the bicycle and the frame of the bicycle. The suspension assembly typically includes a shock absorber configured to absorb forces imparted to the bicycle by bumps or other irregularities of the surface on which the bicycle is being ridden. However, an undesirable consequence of incorporating a suspension assembly in a bicycle is the tendency for the shock absorber to absorb a portion of the power output of a rider of the bicycle. In some instances, i.e. when the rider is standing, the proportion of power absorbed by the shock absorber may be substantial and may drastically reduce the efficiency of the bicycle.
Vehicle shock absorbers utilize inertia valves to sense rapid accelerations generated from a particular part of the vehicle. Inertia valves are also used to change the rate of damping in the shock absorber depending on the magnitude of the acceleration. However, acceleration forces acting on the inertia valve tend to diminish prior to the completion of the surface irregularity that caused the acceleration. Thus, the acceleration force also diminishes prior to the completion of the compression or rebound stroke of the shock absorber caused by the surface irregularity.
One example of the type of shock absorber that utilizes an inertia valve to distinguish rider-induced forces from terrain-induced forces and is described in U.S. Pat. No. 5,823,305. The '305 patent discloses an inertia valve arrangement incorporating a restricted fluid flow path downstream of fluid ports controlled by the inertia valve. The restricted fluid flow path is created between the inertia mass and a shoulder of the main piston of the shock absorber as shown in FIG. 3. Fluid flow through the restricted fluid flow path tends to inhibit premature closing of the inertia valve. However, as also apparent in FIG. 3, fluid flow through the main piston, when the inertia valve is closed, must also pass through a restricted flow path between the inertia valve and the piston. As a result, non-inertia valve fluid flow may be undesirably restricted. The entirety of the '305 patent is hereby incorporated by reference herein.